Anesthesia is seldom a problem

Q: I'm scheduled to have surgery soon, and I have never been under general anesthesia. How can I be sure I won't have a severe reaction to it?

A: Severe reactions to anesthesia, fortunately, are very rare. You may be concerned, in particular, with a severe, sometimes fatal, reaction to anesthetics called malignant hyperthermia. It usually occurs during or after surgery but can occur whenever anesthetic drugs are used. This includes emergency rooms, dental offices and intensive care units.

Malignant hyperthermia is caused by a rare muscle abnormality. In this inherited condition, muscle cells have an abnormal protein on their surfaces. The protein does not greatly affect muscle function. As a result, many people are unaware of this abnormality.

However, when certain general anesthetic drugs interact with the abnormal protein on the muscle cells, they cause the muscles to contract forcefully and keep contracting. This sustained muscle contraction generates a lot of heat.

Symptoms usually occur within the first hour after exposure to the trigger medication. As soon as malignant hyperthermia is suspected, doctors must act quickly. They should immediately stop giving the trigger medication and stop the surgery. Doctors then give the drug dantrolene (Dantrium). Dantrolene relaxes the muscles and stops the dangerous increase in muscle metabolism.

With prompt treatment, symptoms should resolve within 24 hours. But if a severe reaction develops before treatment begins, complications may develop. These can include respiratory or kidney failure.

How can you protect yourself against having malignant hyperthermia if you are scheduled for general anesthesia? It is not practical to test for this condition in everyone who is scheduled for surgery. The abnormal protein can be caused by a number of different genetic defects, and not every person with the abnormal protein has a bad reaction with general anesthesia.

However, you should be tested before surgery if you have:

-âA family history of malignant hyperthermia.

-âA history of heat stroke or hyperthermia after exercise.

-âMuscle abnormalities that may be associated with malignant hyperthermia.

If you have been diagnosed with the disorder, notify your doctor before you undergo any surgery or office-based procedure. Many safe alternative anesthetics are available.

DR. ANTHONY KOMAROFF is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.askdoctork.com.

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